title: The role of different glutamate receptors in the mediation of glutamate-evoked excitation of red nucleus neurons after simulated microgravity in rat.
abstract: The present study investigates changes in red nucleus (RN) neuronal activity and the role of glutamate receptors (GluRs) after simulated microgravity (tail-suspension) in the rat using single-unit recording and microinjection. The results showed that tail-suspension for 3, 7, and 14 days could induce a significant decrease in spontaneous firing rate of RN neurons in a time-dependent manner. Unilateral microinjection of glutamate into the RN significantly increased the firing rate of RN neurons, but the increased firing rate was significantly reduced following tail-suspension time. Microinjection of the NMDA receptor antagonist MK-801 or the non-NMDA receptor antagonist DNQX into the RN blocked this excitatory effect induced by glutamate. However, microinjection of the metabotropic glutamate receptor (mGluR) antagonist (+/-)-MCPG into the RN had no effect. These results suggest that simulated microgravity can reduce excitability of RN neurons following a functional impairment of glutamate receptors. NMDA and non-NMDA receptors, but not mGluRs, are involved in the mediation of glutamate-evoked excitation of RN neurons. The decrease in excitability of RN neurons may be involved in simulated microgravity-induced muscle atrophy.
authors.affiliation: Department of Physiology and Pathophysiology, Xi'an Jiaotong University School of Medicine, Xi'an Yanta Street W 76#, Xi'an, Shaanxi 710061, China.
authors.forename: Jian-Chang
authors.initials: JC
authors.lastname: Yang
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Fan
authors.forename: Xin-Ai
authors.initials: XA
authors.lastname: Song
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
mesh_terms: D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D019417:Hindlimb Suspension; D008845:Microinjections; D009474:Neurons / Q000187:drug effects*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000187:drug effects / Q000502:physiology*; D012012:Red Nucleus / Q000166:cytology / Q000187:drug effects*; D013268:Stimulation, Chemical; D018474:Weightlessness Simulation
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D017470:Receptors, Glutamate; C474696:methyl-(4-carboxyphenyl)glycine; D018698:Glutamic Acid; C056723:FG 9041; D016291:Dizocilpine Maleate; D005998:Glycine